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#1
04-19-2019, 02:53 AM
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Which brake shoe is the primary?
...and is it installed in the front or the rear?
I know what the shop manual shows and I tend to treat that as the bible...but interestingly enough, in my research, it's almost universally said that it's the opposite because 'that's the way that I was taught' back in the day.
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Greg Reid Palmetto, Georgia |
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#2
04-19-2019, 06:01 AM
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The short shoe is the primary and is installed to the front.
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#3
04-19-2019, 07:55 AM
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Frt......as stated above
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 1973 Firebird Navajo Orange w/shaker,1973 400/461,1972 Intake SD CNC'd,1977 Q-Jet 800 CFM w/ Cliffs Kit,Tanks Inc PA4 255 Walbro intank pump ,-8an feed/return,RobbMc Regulator,RobbMc 40 micron filter,253 CFM 6x-8's w/H.S 1:5 Roller Rockers,SD Stump Puller H/R Cam 230/236 @.050 112 lobe separation 565/.570 lift,Crower Solid Rollers,28150 Hedman Headers,3" exhaust,full tailpipes,350 Turbo,9.5" 3200 Converter,3:42 gear,8.5 posi,C/E slide-alinks,Koni adj frt shocks,Best 12.18@110.55 Lookin for 11's
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#4
04-19-2019, 11:37 AM
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Well, that's the answer I'm finding almost 100 percent of the time but the factory service manual shows the long shoe front and calls it primary. ???
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Greg Reid Palmetto, Georgia |
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#5
04-19-2019, 12:28 PM
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Long shoe goes to the rear, regardless of how you name it.
George
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"...out to my ol'55, I pulled away slowly, feeling so holy, god knows i was feeling alive"....written by Tom Wait from the Eagles' Live From The Forum |
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#6
04-19-2019, 12:33 PM
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I remember going through this ... but don't remember the answer .. I ended up going by the instructions included with the shoes .... which I think agreed with the shop manual.
Keep in mind which side is being represented in a photo. A straight on photo of the outside of a right side brake will show the primary shoe on the RIGHT/Front in the picture, in a picture of the LEFT side brake shoes the primary shoe will be on the LEFT/Front in the picture. I think much of the confusion comes from people not realizing, or remember that the pictures might represent LEFT or RIGHT sides of the car. As seen in the photos below. |
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#7
04-19-2019, 12:44 PM
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Quote:
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#8
04-19-2019, 01:08 PM
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What happens if you reverse them ? Dont they grab real hard at first on apply?
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A man who falls for everything stands for nothing. |
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#9
04-19-2019, 02:03 PM
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Quote:
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Jeff 
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#10
04-19-2019, 02:18 PM
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Short guys to the front of the line(ing)
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#11
04-19-2019, 02:58 PM
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Well, it's unanimous.. the factory manual is wrong. It shows the right rear, primary shoe front..but it's the long one. I need to check a few other manuals. Maybe I found something the proofreaders missed..
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Greg Reid Palmetto, Georgia |
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#12
04-19-2019, 03:01 PM
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Short to the front, long to the rear.
The "short" shoe is USUALLY thicker, softer, and lighter-colored. The "long" shoe is USUALLY thinner, harder, and darker-colored. The different materials provide different coefficients of friction, the soft front shoe grabs hard, wears faster, so needs to be thicker in order to have a similar service life to the rear shoe which does most of the actual braking. The soft front shoe's job is to cram the rear shoe into the drum harder than the wheel cylinder is able to. All of this changes if we're not talking about Duo-Servo style brakes. The Leading-Trailing shoe brakes of half-ton pickups since '88, for example; or the "Citation" X-body rear brakes. |
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#13
04-19-2019, 04:02 PM
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Quote:
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#14
04-19-2019, 04:09 PM
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The reason why the short shoe is in the FRONT position is because it is the shoe that activates the Braking Process.
It contacts the Brake Drum first and "Wraps around the Brake Drum Circumference. The Rear Shoe, when the "wrap" is completed) is closest to the fixed "anchor pin" and exerts a high clamping load to the majority of the drums surface. When the Braking Process is completed the springs pull the shoes inward and the drum then moves freely again. THAT is why the smaller surface area shoe is toward the front of the vehicle. It does some of the work but not the majority of the work. If you install the shoes backward you now have a smaller percentage of the braking force applied to the drum due to the smaller area. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
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#15
04-19-2019, 04:15 PM
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Quote:
I checked the 69 and 71 manuals to compare. They show it as it should be. Looks like the 68 photo slipped by the proofreaders as you said.
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Ed 1968 GTO (Thanks Mom) 2006 Silverado 2007 Cadillac SRX 2015 Chevy Express  
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#16
04-19-2019, 04:51 PM
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'66 too... Different photo but same deal... Also, it couldn't be a reverse photo because the e-brake lever is to the rear ... Along with the short shoe.
I don't doubt the experience here but what the heck? Someone else check a 68 manual and see if it's just me.
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Greg Reid Palmetto, Georgia |
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#17
04-20-2019, 04:33 AM
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If you are talking about the photo on page 5 - 6 in the section for "standard brakes" yep, it's wrong, shows the short shoe in back.
If you look at the assembly note on page 5 - 9 it does mention the primary shoes are shorter than the secondary and that they go in front. Reading through it reminded me ... I'm not sure that I checked my adjusting screws to make sure the proper ones were on the left and right side of vehicle. The right side adjusters front and rear have left handed threads. Last edited by dataway; 04-20-2019 at 04:41 AM. |
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#18
04-20-2019, 07:13 AM
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Quote:
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Will Rivera '69 Firebird 400/461, 290+ E D-Ports, HR 230/236, 4l80E, 8.5 Rear, 3.55 gears '64 LeMans 400/461, #16 Heads, HR 230/236, TKO600, 9inch Rear, 3.89 gears '69 LeMans Vert, 350, #47 heads: Non-running project |
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#19
04-20-2019, 07:48 AM
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If I remember correctly, It has been quite a few years since the Pontiac Dealership, (like 40+) when you stick the brake adjusting tool into the slot you grip the teeth of the adjuster wheel and the adjuster tool handle goes down on both sides to adjust tighter. Adjuster wheel goes upward. That would fit with the adjusters having right and left hand threads.
Might have it backward on the direction but do not think so. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
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#20
04-20-2019, 08:05 AM
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The brakes will still apply with the shoes reversed, just not as effectively since they are the sliding-caliper design (fixed upper pin).
Later designs used two pins and were not nearly as effective as the early style, but at least you could pull the drums off after 100,000 miles and the shoes still looked nearly new.......Cliff
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